SO2, silicate clouds, but no CH4 detected in a warm Neptune with JWST MIRI
Bibliographic record
Abstract
Abstract The chemical composition of planetary atmospheres bears the imprint of their formation and evolution1,2. Recently, the significance of photochemistry was highlighted through the assignment of sulphur dioxide (SO2) as carrier of a feature near 4.05 μm in the spectrum of a hot (~1200 K) Saturn-mass planet3-5. However, the prevalence of photochemistry and its impact on the composition and stability of atmospheres remains unknown. Here we report the detection of two fundamental vibration bands of SO2 (~9σ) in the atmosphere of the warm super-Neptune planet6,7 WASP-107b using the Mid-Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST). This discovery establishes WASP-107b as the second irradiated exoplanet with confirmed photochemistry, extending the temperature range of exoplanets exhibiting detected photochemistry from ~1200 K down to ~740 K. Additionally, our spectral analysis reveals the presence of silicate clouds, which are strongly favoured (~7σ) over simpler cloud setups. Furthermore, water (H2O) is detected (~12σ), but methane (CH4) is not. These findings provide evidence of disequilibrium chemistry and indicate a dynamically active atmosphere with a super-solar metallicity. These results highlight the importance of the mid-infrared wavelength range in unravelling the chemical and dynamical processes occurring in exoplanet atmospheres.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".